Thermoplastic polyurethane (TPU)/SBS compatibilized blends have been developed for injectable shoe soles. International Publication No. WO 2008/057881 discloses such compatibilized blends for the manufacturer of articles with good mechanical properties. However, when these blends contain a high amount of the SBS (for example, greater than 20 weight percent), the melt flow index (MFI) typically decreases to values less than 15 g/10 min (5.0 kg, 190° C.), which, in turn, makes the injection molding of such blends very difficult. A common method to increase a composition's MFI is to add oil, or to substitute a part of the dry rubber with a lower viscosity, oil-extended rubber, or with a low molecule weight polymer. However, although these methods improve the MFI, they do not improve, or can even make worse, other properties, like tensile strength, abrasion resistance, and/or tear resistance.
International Publication No. WO 2008/057881 discloses compositions comprising the following: a) at least one olefin-based polymer, at least one halogenated ethylene-based polymer, or at least one elastomer rubber, b) at least one thermoplastic polyurethane, and c) a polydiene-based polyurethane. These compositions can be used to promote adhesion between polar and nonpolar materials, and for the manufacture of articles, such as, films, fibers, sheets, tie layers, tubes, adhesives, dispersions, protective apparel, footwear, coatings, laminates and foams.
U.S. Pat. No. 5,241,004 discloses a sheet or molded article formed from a thermoplastic material comprising the following: a polyurethane, a polyvinyl acetate, and a component selected from an additional thermoplastic material, an elastomer-modified thermoplastic material, a rubber, or combinations thereof. The material is disclosed as having improved melt strength.
U.S. Pat. No. 6,106,952 discloses a thermoplastic polymer composition containing the following: a) 100 parts of a block copolymer comprising an aromatic vinyl block and a conjugated diene block, b) 5 to 200 parts of a polyurethane block copolymer having a thermoplastic polyurethane block, c) 10 to 300 parts of a thermoplastic polyurethane, and d) 10 to 300 parts of a paraffin oil. The composition is used to form laminate structures.
U.S. Pat. No. 6,740,711 discloses a pressure sensitive, hot melt adhesive composition comprising one or more pressure-sensitive, adhesive matrices and at least 0.5 weight percent of a trans-polyoctenamer. The composition can be used for medical, consumer and industrial products.
European Patent Application No. 1902865A1 discloses a pneumatic tire having a rubber component that includes the following: a) 100 parts by weight (phr) of a rubber containing olefin unsaturation, b) from 50 to 120 phr of silica, and c) from 1 to 40 phr of a polyoctenamer. The rubber composition is disclosed as having improved abrasion resistance.
There remains a need for injectable elastomeric compositions for footwear components, such as shoe outsoles, with improved processability, and maintained, or improved, mechanical properties, such as abrasion resistance. There is a further need for such compositions that have an improved balance of processability (as measured by an increased MFI), and abrasion resistance, while not sacrificing other important mechanical properties. These needs and others have been met by the following invention.